1. Technical Field
The present invention relates to a common mode filter and a method of manufacturing the same, and more particularly, to a common mode filter connected with a space in which a magnetic flux is formed and a method of manufacturing the same.
2. Description of the Related Art
In accordance with the development of a technology, electronic devices such as a portable phone, a home appliance, a personal computer (PC), a personal digital assistant (PDA), a liquid crystal display (LCD), and the like, have been changed from an analog scheme into a digital scheme and have been speeded up due to an increase in a data amount to be processed. Therefore, USB 2.0, USB 3.0, and a high-definition multimedia interface (HDMI) have been widely distributed as a high speed signal transmission interface and used in numerous digital devices, such as a personal computer, a high quality digital television, and the like.
Unlike a single-end transmission system generally used for a long period of time, these interfaces adopt a differential signal system that uses a pair of signal lines to transmit a differential signal (differential mode signal). However, the digitized and speeded up electronic devices are sensitive to stimulus from the outside. That is, in the case in which small abnormal voltage and a high frequency noise are introduced from the outside into an internal circuit of the electronic device, a circuit may be damaged and a signal may be distorted.
In order to prevent a circuit breakage or a signal distortion of electronic devices from occurring, a filter is mounted to interrupt the introduction of abnormal voltage and high frequency noise into a circuit. Generally, a common mode filter has been used in a high speed differential signal line, and the like, to remove a common mode noise.
The common mode noise is noise occurring at the differential signal line and the common mode filter removes noises that may not be removed by the existing EMI filter. The common mode filter contributes to improvement in EMC characteristics of a home appliance, and the like, and improvement of antenna characteristics of a cellular phone, and the like.
Referring to Japanese Patent Laid-Open Publication No. 2012-015494, a general common mode filter according to the related art has a structure in which a magnetic substrate is disposed at a lower part thereof, an insulating layer enclosing a coil electrode is stacked thereon, and a magnetic resin composite is disposed on the insulation layer.
The magnetic substrate and the magnetic resin composite may be made a ferrite composition having high permeability, such that the magnetic flux in the vicinity of the coil electrode that is generated from the coil electrode in the foregoing structure continuously flows along the magnetic substrate and the magnetic resin composite.
However, in the structure according to the related art, an insulating layer having low permeability exists in the magnetic substrate and the magnetic resin composite, such that the flow of magnetic flux may be weakened, thereby degrading impedance and cut-off frequency characteristics of the common mode filter.
Further, the magnetic substrate and the magnetic resin composite is made of Ni—Zn-based, Mn—Zn-based, Ni—Zn-based, Ni—Zn—Mg-based, Mn—Mg—Zn-based ferrite or a mixture thereof, whereas the insulating layer may be made of polymer materials, such as epoxy resin, phenol resin, polyimide resin, and the like. As such, cracks or a delamination phenomenon may occur at a boundary surface between the magnetic substrate and the insulating layer and the magnetic resin composite and the insulating layer due to a bonding of heterogeneous materials having different chemical characteristics.